Hi,
I use this computer listed in my system specs only for gaming.(No online) I was thinking about upgrading to a HD5870 card.(HD5970 is too much $) I have been told to get the best Video card I can afford and have just enough CPU and Ram to run it. My question is, will my present CPU and Ram be enough to run this card, or should I be looking at building a newer platform and add a better card later, when the new cards come out?

+1 on Erock's suggestion. Take an asus 5850 so you can voltmod it easier and push it up to 5870 speeds really easily. My 5850 toxic hits 930/1330 on 1.088v so you should be able to even higher w/ voltage pushes

Just depends on how often you upgrade that rig. I would say get the 5870 only because you can't crossfire with that motherboard. This way you've got too much power for now, but enough to last you a good year and a half or so.

Think of this; if you buy a 5870 now, but want to upgrade in maybe 6 months or so, you can add a 5970 to your system(provided you get a new motherboard), by then the 5970's will have come down in price significantly with newer cards coming out. By adding the 5970, it'll be like 5870 tri-fire.

I was thinking of that in a bit. Since this a gaming rig only, then the LGA 1156 platform in my opinion would do. At this point I am not interested in the new Core6 chip, so the LGA 1366 platform would not give me a advantage, except it might be easier to OC(depending on the MoBo). I do not know if the memory would make a big different or not. I would like to stay with a single video card to. Also by that time the price of the two platforms will widen.(I hope)
Thoughts anyone?

At some point when you decide to upgrade your motherboard and CPU, which if I were you I wouldn't right now and wait maybe another 6 months to a year, the 1366 platform is going to be the better choice for you. The 1156 socket is merely a gap, very small at that, between 775(your current) and 1366.